U1000 Nissan GM Fault Code


The trouble code U1000 is a vehicle specific code primarily found on Chevrolet, GMC and Nissan vehicles. It refers to a "Class 2 communications failure." Generally, this code will precede an additional code that identifies the module or area of the failure. The second code may be generic or vehicle specific.



What causes the code?

The cause for this code varies with each vehicle. The second code will identify the defective part or area that the fault has occurred. The code is so specific that the technical service bulletins (TSBs) must be examined not only for the make of vehicle, but for the specific model and options present for an accurate assessment. I have experienced several Nissan vehicles with code U1000 that stood alone. No problems were found in any of the systems, yet the code persisted. Exhibiting no driveability or operational problems, the code was simply ignored.


When is the code detected? 


  • If the U1000 stands alone, no symptoms may be present Symptoms will likely be present 
  • Synonymous with the secondary code indicating a particular failure-a failed climate control module or a failed automatic headlight-dimming module for example 
  • In the case of a known Nissan TSB (technical service bulletin), symptoms may include engine stalling, hesitation, lack of power, failure to start or other potential symptoms.



Description 

All communications through the CAN bus requires a good ground, continuity without shorting, lack of resistance which would cause a drop in voltage and good components.


  • Access all technical service bulletins (TSB) relating to code U1000 and any additional codes for your particular model and option group. 
  • Use the service manual in combination with the TSBs to identify the area or module at fault. Study the method to access the faulty module. 
  • Disconnect the module to isolate it from the CAN bus harness and connector. 
  • Check the CAN bus harness and connector for shorts or opens using a voltmeter. 
  • Follow the directions in the service manual used for determining whether the ECM is at Fault or if the module is to blame.

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